From 35cd39da15f9bf8d55cb3249c6d32cd7756cd21f Mon Sep 17 00:00:00 2001 From: Matt Corallo Date: Tue, 1 Feb 2022 21:57:01 +0000 Subject: [PATCH] Lock outbound channels at 0conf if the peer indicates support for it If our peer sets a minimum depth of 0, and we're set to trusting ourselves to not double-spend our own funding transactions, send a funding_locked message immediately after funding signed. Note that some special care has to be taken around the `channel_state` values - `ChannelFunded` no longer implies the funding transaction is confirmed on-chain. Thus, for example, the should-we-re-broadcast logic has to now accept `channel_state` values greater than `ChannelFunded` as indicating we may still need to re-broadcast our funding tranasction, unless `minimum_depth` is greater than 0. Further note that this starts writing `Channel` objects with a `MIN_SERIALIZATION_VERSION` of 2. Thus, LDK versions prior to 0.0.99 (July 2021) will now refuse to read serialized Channels/ChannelManagers. --- lightning/src/ln/channel.rs | 68 ++++++++++++++--------- lightning/src/ln/channelmanager.rs | 43 ++++++++++---- lightning/src/ln/priv_short_conf_tests.rs | 34 ++++++++++++ lightning/src/util/config.rs | 19 +++++++ 4 files changed, 127 insertions(+), 37 deletions(-) diff --git a/lightning/src/ln/channel.rs b/lightning/src/ln/channel.rs index a0b19920f..f221ee622 100644 --- a/lightning/src/ln/channel.rs +++ b/lightning/src/ln/channel.rs @@ -710,6 +710,11 @@ pub(super) struct Channel { // Our counterparty can offer us SCID aliases which they will map to this channel when routing // outbound payments. These can be used in invoice route hints to avoid explicitly revealing // the channel's funding UTXO. + // + // We also use this when sending our peer a channel_update that isn't to be broadcasted + // publicly - allowing them to re-use their map of SCID -> channel for channel_update -> + // associated channel mapping. + // // We only bother storing the most recent SCID alias at any time, though our counterparty has // to store all of them. latest_inbound_scid_alias: Option, @@ -1987,12 +1992,6 @@ impl Channel { if msg.minimum_depth > peer_limits.max_minimum_depth { return Err(ChannelError::Close(format!("We consider the minimum depth to be unreasonably large. Expected minimum: ({}). Actual: ({})", peer_limits.max_minimum_depth, msg.minimum_depth))); } - if msg.minimum_depth == 0 { - // Note that if this changes we should update the serialization minimum version to - // indicate to older clients that they don't understand some features of the current - // channel. - return Err(ChannelError::Close("Minimum confirmation depth must be at least 1".to_owned())); - } if let Some(ty) = &msg.channel_type { if *ty != self.channel_type { @@ -2029,7 +2028,12 @@ impl Channel { self.counterparty_selected_channel_reserve_satoshis = Some(msg.channel_reserve_satoshis); self.counterparty_htlc_minimum_msat = msg.htlc_minimum_msat; self.counterparty_max_accepted_htlcs = msg.max_accepted_htlcs; - self.minimum_depth = Some(msg.minimum_depth); + + if peer_limits.trust_own_funding_0conf { + self.minimum_depth = Some(msg.minimum_depth); + } else { + self.minimum_depth = Some(cmp::max(1, msg.minimum_depth)); + } let counterparty_pubkeys = ChannelPublicKeys { funding_pubkey: msg.funding_pubkey, @@ -2169,7 +2173,7 @@ impl Channel { /// Handles a funding_signed message from the remote end. /// If this call is successful, broadcast the funding transaction (and not before!) - pub fn funding_signed(&mut self, msg: &msgs::FundingSigned, best_block: BestBlock, logger: &L) -> Result<(ChannelMonitor, Transaction), ChannelError> where L::Target: Logger { + pub fn funding_signed(&mut self, msg: &msgs::FundingSigned, best_block: BestBlock, logger: &L) -> Result<(ChannelMonitor, Transaction, Option), ChannelError> where L::Target: Logger { if !self.is_outbound() { return Err(ChannelError::Close("Received funding_signed for an inbound channel?".to_owned())); } @@ -2238,7 +2242,7 @@ impl Channel { log_info!(logger, "Received funding_signed from peer for channel {}", log_bytes!(self.channel_id())); - Ok((channel_monitor, self.funding_transaction.as_ref().cloned().unwrap())) + Ok((channel_monitor, self.funding_transaction.as_ref().cloned().unwrap(), self.check_get_funding_locked(0))) } /// Handles a funding_locked message from our peer. If we've already sent our funding_locked @@ -3540,12 +3544,13 @@ impl Channel { /// monitor update failure must *not* have been sent to the remote end, and must instead /// have been dropped. They will be regenerated when monitor_updating_restored is called. pub fn monitor_update_failed(&mut self, resend_raa: bool, resend_commitment: bool, - mut pending_forwards: Vec<(PendingHTLCInfo, u64)>, + resend_funding_locked: bool, mut pending_forwards: Vec<(PendingHTLCInfo, u64)>, mut pending_fails: Vec<(HTLCSource, PaymentHash, HTLCFailReason)>, mut pending_finalized_claimed_htlcs: Vec ) { self.monitor_pending_revoke_and_ack |= resend_raa; self.monitor_pending_commitment_signed |= resend_commitment; + self.monitor_pending_funding_locked |= resend_funding_locked; self.monitor_pending_forwards.append(&mut pending_forwards); self.monitor_pending_failures.append(&mut pending_fails); self.monitor_pending_finalized_fulfills.append(&mut pending_finalized_claimed_htlcs); @@ -3559,9 +3564,18 @@ impl Channel { assert_eq!(self.channel_state & ChannelState::MonitorUpdateFailed as u32, ChannelState::MonitorUpdateFailed as u32); self.channel_state &= !(ChannelState::MonitorUpdateFailed as u32); - let funding_broadcastable = if self.channel_state & (ChannelState::FundingSent as u32) != 0 && self.is_outbound() { - self.funding_transaction.take() - } else { None }; + // If we're past (or at) the FundingSent stage on an outbound channel, try to + // (re-)broadcast the funding transaction as we may have declined to broadcast it when we + // first received the funding_signed. + let mut funding_broadcastable = + if self.is_outbound() && self.channel_state & !MULTI_STATE_FLAGS >= ChannelState::FundingSent as u32 { + self.funding_transaction.take() + } else { None }; + // That said, if the funding transaction is already confirmed (ie we're active with a + // minimum_depth over 0) don't bother re-broadcasting the confirmed funding tx. + if self.channel_state & !MULTI_STATE_FLAGS >= ChannelState::ChannelFunded as u32 && self.minimum_depth != Some(0) { + funding_broadcastable = None; + } // We will never broadcast the funding transaction when we're in MonitorUpdateFailed (and // we assume the user never directly broadcasts the funding transaction and waits for us to @@ -3570,7 +3584,8 @@ impl Channel { // the funding transaction confirmed before the monitor was persisted, or // * a 0-conf channel and intended to send the funding_locked before any broadcast at all. let funding_locked = if self.monitor_pending_funding_locked { - assert!(!self.is_outbound(), "Funding transaction broadcast by the local client before it should have - LDK didn't do it!"); + assert!(!self.is_outbound() || self.minimum_depth == Some(0), + "Funding transaction broadcast by the local client before it should have - LDK didn't do it!"); self.monitor_pending_funding_locked = false; let next_per_commitment_point = self.holder_signer.get_per_commitment_point(self.cur_holder_commitment_transaction_number, &self.secp_ctx); Some(msgs::FundingLocked { @@ -4552,6 +4567,11 @@ impl Channel { self.channel_state >= ChannelState::FundingSent as u32 } + /// Returns true if our funding_locked has been sent + pub fn is_our_funding_locked(&self) -> bool { + (self.channel_state & ChannelState::OurFundingLocked as u32) != 0 || self.channel_state >= ChannelState::ChannelFunded as u32 + } + /// Returns true if our peer has either initiated or agreed to shut down the channel. pub fn received_shutdown(&self) -> bool { (self.channel_state & ChannelState::RemoteShutdownSent as u32) != 0 @@ -4582,7 +4602,7 @@ impl Channel { } fn check_get_funding_locked(&mut self, height: u32) -> Option { - if self.funding_tx_confirmation_height == 0 { + if self.funding_tx_confirmation_height == 0 && self.minimum_depth != Some(0) { return None; } @@ -4759,9 +4779,9 @@ impl Channel { // close the channel and hope we can get the latest state on chain (because presumably // the funding transaction is at least still in the mempool of most nodes). // - // Note that ideally we wouldn't force-close if we see *any* reorg on a 1-conf channel, - // but not doing so may lead to the `ChannelManager::short_to_id` map being - // inconsistent, so we currently have to. + // Note that ideally we wouldn't force-close if we see *any* reorg on a 1-conf or + // 0-conf channel, but not doing so may lead to the `ChannelManager::short_to_id` map + // being inconsistent, so we currently have to. if funding_tx_confirmations == 0 && self.funding_tx_confirmed_in.is_some() { let err_reason = format!("Funding transaction was un-confirmed. Locked at {} confs, now have {} confs.", self.minimum_depth.unwrap(), funding_tx_confirmations); @@ -5620,7 +5640,7 @@ impl Channel { } const SERIALIZATION_VERSION: u8 = 2; -const MIN_SERIALIZATION_VERSION: u8 = 1; +const MIN_SERIALIZATION_VERSION: u8 = 2; impl_writeable_tlv_based_enum!(InboundHTLCRemovalReason,; (0, FailRelay), @@ -5685,12 +5705,10 @@ impl Writeable for Channel { self.user_id.write(writer)?; - // Write out the old serialization for the config object. This is read by version-1 - // deserializers, but we will read the version in the TLV at the end instead. - self.config.forwarding_fee_proportional_millionths.write(writer)?; - self.config.cltv_expiry_delta.write(writer)?; - self.config.announced_channel.write(writer)?; - self.config.commit_upfront_shutdown_pubkey.write(writer)?; + // Version 1 deserializers expected to read parts of the config object here. Version 2 + // deserializers (0.0.99) now read config through TLVs, and as we now require them for + // `minimum_depth` we simply write dummy values here. + writer.write_all(&[0; 8])?; self.channel_id.write(writer)?; (self.channel_state | ChannelState::PeerDisconnected as u32).write(writer)?; diff --git a/lightning/src/ln/channelmanager.rs b/lightning/src/ln/channelmanager.rs index 239b45ebf..5f65a66ce 100644 --- a/lightning/src/ln/channelmanager.rs +++ b/lightning/src/ln/channelmanager.rs @@ -1286,7 +1286,7 @@ macro_rules! remove_channel { } macro_rules! handle_monitor_err { - ($self: ident, $err: expr, $short_to_id: expr, $chan: expr, $action_type: path, $resend_raa: expr, $resend_commitment: expr, $failed_forwards: expr, $failed_fails: expr, $failed_finalized_fulfills: expr, $chan_id: expr) => { + ($self: ident, $err: expr, $short_to_id: expr, $chan: expr, $action_type: path, $resend_raa: expr, $resend_commitment: expr, $resend_funding_locked: expr, $failed_forwards: expr, $failed_fails: expr, $failed_finalized_fulfills: expr, $chan_id: expr) => { match $err { ChannelMonitorUpdateErr::PermanentFailure => { log_error!($self.logger, "Closing channel {} due to monitor update ChannelMonitorUpdateErr::PermanentFailure", log_bytes!($chan_id[..])); @@ -1324,13 +1324,13 @@ macro_rules! handle_monitor_err { if !$resend_raa { debug_assert!($action_type == RAACommitmentOrder::CommitmentFirst || !$resend_commitment); } - $chan.monitor_update_failed($resend_raa, $resend_commitment, $failed_forwards, $failed_fails, $failed_finalized_fulfills); + $chan.monitor_update_failed($resend_raa, $resend_commitment, $resend_funding_locked, $failed_forwards, $failed_fails, $failed_finalized_fulfills); (Err(MsgHandleErrInternal::from_chan_no_close(ChannelError::Ignore("Failed to update ChannelMonitor".to_owned()), *$chan_id)), false) }, } }; - ($self: ident, $err: expr, $channel_state: expr, $entry: expr, $action_type: path, $resend_raa: expr, $resend_commitment: expr, $failed_forwards: expr, $failed_fails: expr, $failed_finalized_fulfills: expr) => { { - let (res, drop) = handle_monitor_err!($self, $err, $channel_state.short_to_id, $entry.get_mut(), $action_type, $resend_raa, $resend_commitment, $failed_forwards, $failed_fails, $failed_finalized_fulfills, $entry.key()); + ($self: ident, $err: expr, $channel_state: expr, $entry: expr, $action_type: path, $resend_raa: expr, $resend_commitment: expr, $resend_funding_locked: expr, $failed_forwards: expr, $failed_fails: expr, $failed_finalized_fulfills: expr) => { { + let (res, drop) = handle_monitor_err!($self, $err, $channel_state.short_to_id, $entry.get_mut(), $action_type, $resend_raa, $resend_commitment, $resend_funding_locked, $failed_forwards, $failed_fails, $failed_finalized_fulfills, $entry.key()); if drop { $entry.remove_entry(); } @@ -1338,16 +1338,19 @@ macro_rules! handle_monitor_err { } }; ($self: ident, $err: expr, $channel_state: expr, $entry: expr, $action_type: path, $chan_id: expr, COMMITMENT_UPDATE_ONLY) => { { debug_assert!($action_type == RAACommitmentOrder::CommitmentFirst); - handle_monitor_err!($self, $err, $channel_state, $entry, $action_type, false, true, Vec::new(), Vec::new(), Vec::new(), $chan_id) + handle_monitor_err!($self, $err, $channel_state, $entry, $action_type, false, true, false, Vec::new(), Vec::new(), Vec::new(), $chan_id) } }; ($self: ident, $err: expr, $channel_state: expr, $entry: expr, $action_type: path, $chan_id: expr, NO_UPDATE) => { - handle_monitor_err!($self, $err, $channel_state, $entry, $action_type, false, false, Vec::new(), Vec::new(), Vec::new(), $chan_id) + handle_monitor_err!($self, $err, $channel_state, $entry, $action_type, false, false, false, Vec::new(), Vec::new(), Vec::new(), $chan_id) + }; + ($self: ident, $err: expr, $channel_state: expr, $entry: expr, $action_type: path, $resend_funding_locked: expr, OPTIONALLY_RESEND_FUNDING_LOCKED) => { + handle_monitor_err!($self, $err, $channel_state, $entry, $action_type, false, false, $resend_funding_locked, Vec::new(), Vec::new(), Vec::new()) }; ($self: ident, $err: expr, $channel_state: expr, $entry: expr, $action_type: path, $resend_raa: expr, $resend_commitment: expr) => { - handle_monitor_err!($self, $err, $channel_state, $entry, $action_type, $resend_raa, $resend_commitment, Vec::new(), Vec::new(), Vec::new()) + handle_monitor_err!($self, $err, $channel_state, $entry, $action_type, $resend_raa, $resend_commitment, false, Vec::new(), Vec::new(), Vec::new()) }; ($self: ident, $err: expr, $channel_state: expr, $entry: expr, $action_type: path, $resend_raa: expr, $resend_commitment: expr, $failed_forwards: expr, $failed_fails: expr) => { - handle_monitor_err!($self, $err, $channel_state, $entry, $action_type, $resend_raa, $resend_commitment, $failed_forwards, $failed_fails, Vec::new()) + handle_monitor_err!($self, $err, $channel_state, $entry, $action_type, $resend_raa, $resend_commitment, false, $failed_forwards, $failed_fails, Vec::new()) }; } @@ -4268,7 +4271,7 @@ impl ChannelMana // hasn't persisted to disk yet - we can't lose money on a transaction that we haven't // accepted payment from yet. We do, however, need to wait to send our funding_locked // until we have persisted our monitor. - chan.monitor_update_failed(false, false, Vec::new(), Vec::new(), Vec::new()); + chan.monitor_update_failed(false, false, false, Vec::new(), Vec::new(), Vec::new()); }, } } @@ -4299,12 +4302,12 @@ impl ChannelMana if chan.get().get_counterparty_node_id() != *counterparty_node_id { return Err(MsgHandleErrInternal::send_err_msg_no_close("Got a message for a channel from the wrong node!".to_owned(), msg.channel_id)); } - let (monitor, funding_tx) = match chan.get_mut().funding_signed(&msg, best_block, &self.logger) { + let (monitor, funding_tx, funding_locked) = match chan.get_mut().funding_signed(&msg, best_block, &self.logger) { Ok(update) => update, Err(e) => try_chan_entry!(self, Err(e), channel_state, chan), }; if let Err(e) = self.chain_monitor.watch_channel(chan.get().get_funding_txo().unwrap(), monitor) { - let mut res = handle_monitor_err!(self, e, channel_state, chan, RAACommitmentOrder::RevokeAndACKFirst, false, false); + let mut res = handle_monitor_err!(self, e, channel_state, chan, RAACommitmentOrder::RevokeAndACKFirst, funding_locked.is_some(), OPTIONALLY_RESEND_FUNDING_LOCKED); if let Err(MsgHandleErrInternal { ref mut shutdown_finish, .. }) = res { // We weren't able to watch the channel to begin with, so no updates should be made on // it. Previously, full_stack_target found an (unreachable) panic when the @@ -4315,6 +4318,9 @@ impl ChannelMana } return res } + if let Some(msg) = funding_locked { + send_funding_locked!(channel_state.short_to_id, channel_state.pending_msg_events, chan.get(), msg); + } funding_tx }, hash_map::Entry::Vacant(_) => return Err(MsgHandleErrInternal::send_err_msg_no_close("Failed to find corresponding channel".to_owned(), msg.channel_id)) @@ -4665,7 +4671,7 @@ impl ChannelMana } else { if let Err(e) = handle_monitor_err!(self, e, channel_state, chan, RAACommitmentOrder::CommitmentFirst, false, - raa_updates.commitment_update.is_some(), + raa_updates.commitment_update.is_some(), false, raa_updates.accepted_htlcs, raa_updates.failed_htlcs, raa_updates.finalized_claimed_htlcs) { break Err(e); @@ -5520,6 +5526,19 @@ where } } } + if channel.is_our_funding_locked() { + if let Some(real_scid) = channel.get_short_channel_id() { + // If we sent a 0conf funding_locked, and now have an SCID, we add it + // to the short_to_id map here. Note that we check whether we can relay + // using the real SCID at relay-time (i.e. enforce option_scid_alias + // then), and if the funding tx is ever un-confirmed we force-close the + // channel, ensuring short_to_id is always consistent. + let scid_insert = short_to_id.insert(real_scid, channel.channel_id()); + assert!(scid_insert.is_none() || scid_insert.unwrap() == channel.channel_id(), + "SCIDs should never collide - ensure you weren't behind by a full {} blocks when creating channels", + fake_scid::MAX_SCID_BLOCKS_FROM_NOW); + } + } } else if let Err(reason) = res { update_maps_on_chan_removal!(self, short_to_id, channel); // It looks like our counterparty went on-chain or funding transaction was diff --git a/lightning/src/ln/priv_short_conf_tests.rs b/lightning/src/ln/priv_short_conf_tests.rs index 47e2fb33e..48dab6a22 100644 --- a/lightning/src/ln/priv_short_conf_tests.rs +++ b/lightning/src/ln/priv_short_conf_tests.rs @@ -564,3 +564,37 @@ fn test_scid_alias_returned() { PaymentFailedConditions::new().blamed_scid(last_hop[0].inbound_scid_alias.unwrap()) .blamed_chan_closed(false).expected_htlc_error_data(0x1000|12, &err_data)); } + +#[test] +fn test_simple_0conf_channel() { + // If our peer tells us they will accept our channel with 0 confs, and we funded the channel, + // we should trust the funding won't be double-spent (assuming `trust_own_funding_0conf` is + // set)! + + let chanmon_cfgs = create_chanmon_cfgs(2); + let node_cfgs = create_node_cfgs(2, &chanmon_cfgs); + let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]); + let nodes = create_network(2, &node_cfgs, &node_chanmgrs); + + nodes[0].node.create_channel(nodes[1].node.get_our_node_id(), 100000, 10001, 42, None).unwrap(); + let open_channel = get_event_msg!(nodes[0], MessageSendEvent::SendOpenChannel, nodes[1].node.get_our_node_id()); + + nodes[1].node.handle_open_channel(&nodes[0].node.get_our_node_id(), InitFeatures::known(), &open_channel); + let mut accept_channel = get_event_msg!(nodes[1], MessageSendEvent::SendAcceptChannel, nodes[0].node.get_our_node_id()); + accept_channel.minimum_depth = 0; + nodes[0].node.handle_accept_channel(&nodes[1].node.get_our_node_id(), InitFeatures::known(), &accept_channel); + + let (temporary_channel_id, tx, _) = create_funding_transaction(&nodes[0], &nodes[1].node.get_our_node_id(), 100000, 42); + nodes[0].node.funding_transaction_generated(&temporary_channel_id, &nodes[1].node.get_our_node_id(), tx.clone()).unwrap(); + let funding_created = get_event_msg!(nodes[0], MessageSendEvent::SendFundingCreated, nodes[1].node.get_our_node_id()); + + nodes[1].node.handle_funding_created(&nodes[0].node.get_our_node_id(), &funding_created); + check_added_monitors!(nodes[1], 1); + let funding_signed = get_event_msg!(nodes[1], MessageSendEvent::SendFundingSigned, nodes[0].node.get_our_node_id()); + + nodes[0].node.handle_funding_signed(&nodes[1].node.get_our_node_id(), &funding_signed); + check_added_monitors!(nodes[0], 1); + + let as_funding_locked = get_event_msg!(nodes[0], MessageSendEvent::SendFundingLocked, nodes[1].node.get_our_node_id()); + nodes[1].node.handle_funding_locked(&nodes[0].node.get_our_node_id(), &as_funding_locked); +} diff --git a/lightning/src/util/config.rs b/lightning/src/util/config.rs index 3868d29aa..4d1c7c99a 100644 --- a/lightning/src/util/config.rs +++ b/lightning/src/util/config.rs @@ -159,6 +159,24 @@ pub struct ChannelHandshakeLimits { /// /// Default value: 144, or roughly one day and only applies to outbound channels. pub max_minimum_depth: u32, + /// Whether we implicitly trust funding transactions generated by us for our own outbound + /// channels to not be double-spent. + /// + /// If this is set, we assume that our own funding transactions are *never* double-spent, and + /// thus we can trust them without any confirmations. This is generally a reasonable + /// assumption, given we're the only ones who could ever double-spend it (assuming we have sole + /// control of the signing keys). + /// + /// You may wish to un-set this if you allow the user to (or do in an automated fashion) + /// double-spend the funding transaction to RBF with an alternative channel open. + /// + /// This only applies if our counterparty set their confirmations-required value to 0, and we + /// always trust our own funding transaction at 1 confirmation irrespective of this value. + /// Thus, this effectively acts as a `min_minimum_depth`, with the only possible values being + /// `true` (0) and `false` (1). + /// + /// Default value: true + pub trust_own_funding_0conf: bool, /// Set to force an incoming channel to match our announced channel preference in /// [`ChannelConfig::announced_channel`]. /// @@ -187,6 +205,7 @@ impl Default for ChannelHandshakeLimits { min_max_htlc_value_in_flight_msat: 0, max_channel_reserve_satoshis: ::max_value(), min_max_accepted_htlcs: 0, + trust_own_funding_0conf: true, max_minimum_depth: 144, force_announced_channel_preference: true, their_to_self_delay: MAX_LOCAL_BREAKDOWN_TIMEOUT, -- 2.39.5